In the prior art for concentrating juices, multiple-effect concentration plants are normally used in which concentration is achieved by evaporation.
Multiple-effect concentration plants used for juices and purees of fruit and vegetables are normally realised using different types of functions, in particular forced-circulation evaporators and falling-film evaporators.
In general, each concentration effect avails of a vertical tube bundle in which a plurality of tubes is arranged, ends of which are keyed on two parallel plates, respectively an upper plate and a lower plate, such that the upper ends of the tubes open at an inlet zone of the product while lower ends thereof open into a bottom zone of the evaporator, the separation chamber, in which the product loses water by flash evaporation, and cools; the product is then sent on to further work stations.
The tubes are closed in a sheath, generally cylindrical and delimited by the two parallel plates, internally of which a heating fluid circulates, which is generally steam. The external surface of the tubes is struck by the heating fluid while the internal surface thereof is flowed-through by the product which heats up and loses water in the form of steam, and thus becomes more concentrated.
In forced-circulation evaporators the product completely fills the inside of the tubes, while, in the case of falling-film evaporators, the product forms a thin descending film on the internal part of the tube.
In these plants the tube bundle can be divided into two or more sectors which are arranged in series such that the product which falls from the first sector and reaches the separation chamber is returned to the top of the tube bundle and is made to descend in the subsequent sectors.
The product is then extracted from the separation chamber once it has passed through the final sector. These plants and the functioning thereof are known in the prior art.
The aim of the present invention is to realise a concentration plant which is of simpler construction with respect to the known plants, which is simple to regulate and in which it is possible to obtained various types of functioning in accordance with the viscosity of the products being worked.
An advantage of the invention is that it enables concentrating products having a broad range of viscosity.
A further advantage of the invention is that it reduces the energy consumption required for plant functioning.
These aims and advantages and others besides are all attained by the invention as it is characterised in the following claims.